As a rule, in continuous casting installations, especially continuous steel casting installations, it is necessary from time to time to replace a mould or at least a component of a mould. Thus, for example, when the cavity of a mould is subjected constantly to the effects of strand solidification, the wall defining the mould cavity eventually begins to exhibit wear phenomena and has to be repaired or replaced.
Accidents occurring during casting operation, such as perforation of a strand shell or overflow of the metal melt over the pouring opening of the mould, lead, as a rule, to an interruption in casting operation of the relevant mould. In general, parts of the continuous casting installation, in particular the mould or parts of the mould and strand guiding devices below the mould have to be freed from solidified metal or even replaced before casting operation may be resumed.
Moulds are conventionally supported in a continuous casting installation by a holding device which is so constructed that the moulds may oscillate in a casting position. The holding device usually takes the form of an oscillating table, which is accessible from above for the purpose of installing and removing a mould. In a multi-strand installation with moulds having vertical or oblique cavities, tundishes are arranged above the moulds during casting operation, molten metal being poured from these tundishes into the mould cavities, wherein a plurality of moulds is conventionally supplied with melt from one tundish comprising several outlets. An accident entailing replacement of a mould requires the casting operation to be stopped at the mould affected by the accident and consequently results in a reduction in the casting yield of the multi-strand installation, since the tundish blocks access to the moulds from above and the necessary mould exchange is only possible in a break in casting after removal of the tundish.
A continuous casting installation is known from U.S. Pat. No. 3, 273,208 which is suitable for long sequential casts and is provided with an apparatus for quick mould replacement. The mould is arranged on a sliding table which is capable of rectilinear, horizontal displacement and interacts with a mould delivery carriage displaceable perpendicularly thereto or with a turntable. The displaceable sliding table requires open holes in the teeming platform floor along the displacement path, which holes are undesirable for reasons of safety. If a turntable is used in conjunction with multi-strand installations, large gaps are needed between strands, making large tundishes necessary. Installation of this swapping device in multi-strand installations leads not only to high structural complexity but also to high operating costs, stemming from maintenance of the wear-prone tundishes. Moreover, when molten metal is poured from one tundish into a plurality of moulds, variations occur in the casting parameters, for example differences in casting temperature or in the superheating temperature in the various moulds. These variations are generally greater, the larger the strand spacing and lead to unacceptable variations in the quality of the strands withdrawn from the different moulds.
JOS 62-9749, discloses a device for exchanging a mould in a continuous casting installation equipped with an oscillatory holding device for the mould. The holding device comprises a deck, to which the mould may be fixed in an operating position and the height of which may be adjusted by means of two lever systems provided with independent drives. A first lever system enables the deck to be lowered and raised and serves as a conveying device for conveying the mould out of the operating position into a second position, in which the mould may be gripped by a second conveying device below the teeming platform, lifted from the deck and conveyed on further. A second lever system permits oscillation of the mould about the position set by the first lever system, the assembly comprising the mould, the deck and the first lever system being set in motion as a whole by means of the second lever system. This design has the disadvantage that, during casting operation, a relatively large overall weight has to be kept in motion in order for the mould to oscillate and that the first lever system has to undergo complex stabilisation with respect to the vibrations transmitted by the second lever system, in order to be able to maintain the casting conditions in a controlled manner over a relatively long period. Furthermore, in the initial phase of mould replacement a relatively large weight in addition to the mould has to be moved by means of the conveying device.
A mould is known from DE 32 07 149, which is attached in releasable manner to an oscillating elevating platform and comprises a water chamber, upper and lower flange plates, a water conveying jacket and a mould tube. The flange plates, the mould tube and the water conveying jacket form a unit, held together by connecting members, which may, am a compact, adjusted structural component, be withdrawn upwards out of the water chamber by a crane or introduced from above into the water chamber and can therefore only be exchanged above the mould during a break in casting and after removal of the tundish.
LU 84 507 discloses a multistrand casting installation with an arrangement of moulds in which each mould, including all its accessories, such as in particular the mould oscillating device, is arranged on a frame which is mounted on a lowerable platform so as to be displaceable in the longitudinal direction. When the platform has been lowered, the mould may be moved, together with the oscillating device, which consists of an oscillating mechanism and a drive motor, along the platform to a position below the operating position, where it may be separated from the oscillating device and then exchanged. With this arrangement too, a relatively large weight has to be moved before the mould may be exchanged.
The object of the invention is to avoid the disadvantages of the known devices and to provide a structurally simplified device and a method for exchanging a replaceable part of a mould arrangement in a continuous casting installation, the intention being to make it possible to carry out the replacement process on an individual selected mould in a multi-strand installation while the casting operation remains active.